Logically!
OK, here's my response to your 'logic':
-An alien is a non-human being not born on Earth.
-Jesus Christ was a man, born on Earth.
-Jesus Christ was not an alien.
-Jesus Christ was fully man, and fully God.
-Conclusion: God is not an alien.
See? I can be all logical and crap too.

And yet, that doesn't change the fact that this is a dumb discussion.
Of course, I could continue and talk about how your parallel is stupid, because we don't know if we can fight aliens, but we know we can't fight God, and how there was no way for man to fight back in the Flood story, or how there's no mention of
why the aliens/God are attacking, or....well, you see my point. Or more likely, you don't, and you'll continue to stubbornly insist that you've thought up some brilliant, shocking critique of Christianity.